Etching apparatus

ABSTRACT

Disclosed is an etching apparatus enabling to increase productivity of etching glass substrates. The present invention includes an etching bath having an etchant, a plurality of sensors inside the etching bath detecting a level of the etchant, and a deionized water tube spraying a deionized water to the sensors.

This application claims the benefit of the Korean Application No.P2001-88521 filed on Dec. 29, 2001, which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an etching apparatus for a liquidcrystal display device, and more particularly, to an etching apparatusenabling to increase productivity by sensing a level of an etchant usinga contact sensor and preventing the sensor from being degraded byparticles.

2. Discussion of the Related Art

Recently, many efforts have been made to research and develop variousflat display panels such as LCD (liquid crystal display), PDP (plasmadisplay panel), ELD (electroluminescent display), VFD (vacuumfluorescent display), and the like. LCD is practically used because ofthe characteristics or advantages of high quality image and low powerconsumption.

The liquid crystal display device includes lower and upper substratesconfronting each other to leave a predetermined interval from each otherand a liquid crystal layer formed between the substrates. A black matrixand a color filter layer are formed on the upper substrate. And, on thelower substrate formed are a plurality of gate and data lines arrangedhorizontally and vertically with a predetermined interval from eachother to define pixel areas and thin film transistors and pixelelectrodes formed in the pixel areas, respectively.

Lightweight and compact size are demanded for the liquid crystal displaydevice to be applied to portable TV set, notebook computer, and thelike. Yet, the structure or technology of the liquid crystal displaydevice has limitation for the lightweight and compact size. However, theglass substrate as a basic element of the liquid crystal display deviceis the heaviest in the components of the liquid crystal display device.Hence, many efforts are made to reduce the weight of the glasssubstrate.

In order to reduce the weight of the glass substrate, a thickness of theglass substrate should be decreased. Yet, a physical force isoccasionally applied to the glass substrate in the process offabricating the liquid crystal display device. And, the glass substrateundergoes a number of heating and cooling processes. Hence, the thinglass becomes easy to be broken. Recently, used is a new methodincluding the steps of using a thick glass substrate in the early stageof process and thinning the glass substrate in the later process.Namely, devices and color filters are formed on thick glass substratesto prepare upper and lower glass substrates, the upper and lower glasssubstrates are bonded to each other, and then outer surfaces of theglass substrates are etched to reduce an overall thickness of the liquidcrystal display device.

Generally, the glass substrate is etched by wet etching carried out in amanner that the glass substrate is dipped in a bath filled with anetchant of strong acid etching a surface of the glass substrate.

However, such a method of wet etching makes the uneven surface of thesubstrate since particles generated from the etching process sticks tothe substrate. Moreover, if the supply of the etchant fails to becontrolled, the glass substrate is etched in part to generate thefailure caused by the difference between the etched and non-etchedportions.

In order to overcome such problems, a supply flow of an etchant iscontrolled using an etching apparatus equipped with a sensor enabling tosense the supply flow of the etchant.

An etching apparatus according to a related art is explained byreferring to the attached drawings as follows.

FIG. 1 illustrates a schematic cross-sectional view of an etchingapparatus according to a related art.

Referring to FIG. 1, an etching apparatus according to a related artincludes an etching bath 1 having an etchant, a bubble plate 3 installedat a lower side inside the etching bath 1 to generate bubbles by a gasor an air supplied from outside to remove particles on a surface of asubstrate which is being etched, a porous plate 5 installed on thebubble plate 3 to support a glass substrate (not shown in the drawing)to be etched, a supply pipe 15 supplying the bubble plate 3 with the airor the gas (N₂), a buffer tank 13 discharging and filtering the etchantused for etching from the etching bath 1 through an etchant dischargingpipe 11 for temporary storage, a deionized water supply unit 17supplying deionized water, an undiluted etchant supply unit 19 supplyingan undiluted etchant, an etchant supply tank 9 supplied with thedeionized water and the undiluted etchant by the deionized water and theundiluted etchant supply units 17 and 19 and mixing the supplieddeionized water and crude etchant with each other to supply the etchingbath 1 with the etchant having a predetermined concentration through anetchant supply pipe 7, and an etchant detecting sensor 21 installed atan upper side of an inner wall of the etching bath 1 to detect a levelof the etchant supplied to the etching bath 1.

In this case, the etchant supply tank 9 mixes the etchant using thedeionized water supplied by the deionized water supply unit 17 and theundiluted etchant(ex. HF) supplied by the undiluted etchant supply unit19, or is supplied with the etchant, which is recycled after completionof etching, from the buffer tank 13, to make the etchant having thepredetermined concentration to be sent to the etching bath 1.

A plurality of glass substrate(not shown in the drawing) that will beetched are stood straight on the porous plate 5 with a predeterminedinterval from each other, and are dipped in the etchant filling theetching bath 1 for etching. Bubbles are generated through the bubbleplate 3 and the etchant circulates uniformly by the bubbles. Thus, theglass substrates can be etched evenly. And, the bubbles detach theparticles caused by the etching process from surfaces of the substrates.

Moreover, a guard 2 is formed on the inner wall of the etching bath 1 toprotect the etchant detect sensor 21, and has a structure that front andrear sides in the drawing are open. If the etchant is supplied over apredetermined level, the etchant is put inside the guard 2.

In this case, when the etchant supplied from the etchant supply tank 9to the etching bath 1 is supplied to the amount that the glasssubstrates are dipped in the etchant in part, the glass substrates failto be etched uniformly but the portions of the glass substrates dippedin the etchant are etched only, whereby etch failure occurs. Hence, theetchant should be supplied to the level enabling to have the glasssubstrates dipped in the etchant entirely.

Therefore, it is able to control the supply of the etchant to theetching bath 1 stably using the etchant detect sensor 21 installed atthe upper inner wall of the etching bath 1 before the etch is carriedout. Moreover, it is also able to check the discharged state when theetchant is drained from the etching bath 1 after the completion of theetch.

Namely, the etchant detect sensor 21 according to the related art is alevel sensor using an air pressure difference according to height of theetchant and the nitrogen gas (N₂) supplied regularly, and includes, asshown in FIG. 2, a magnetic valve 22 controlling a supply of a nitrogengas for constant pressures of three tubes by receiving a nitrogen gas(N₂) of low pressure from a portion of the air supply pipe (‘15’ in FIG.1), a plurality of nitrogen pressure difference sensors 23 a, 23 b, and23 c detecting a pressure difference of the nitrogen gas cut off by anetchant 25 supplied inside an etching bath by having the nitrogen gasflow, and “L(low)”, “H(high)”, and “HH(high high)” nitrogen tubes 24 a,24 b, and 24 c receiving the nitrogen gas at low pressure to dischargethe nitrogen gas in accordance with height.

Operation of the above-constituted nitrogen pressure difference sensoris explained in detail as follows.

First of all, when the etchant 25 is supplied inside the etching bath 1for etching the glass substrate, the etching apparatus according to therelated art detects that the nitrogen gas fails to be discharged sincethe “L” nitrogen tube 24 a of the etchant detect sensor is blocked bythe etchant having been supplied over a predetermined level, therebyrecognizing that the etchant is being supplied inside the etching bath1. The etching apparatus keeps supplying the etchant even if thenitrogen gas is unable to be discharged due to the blocked “L” nitrogentube 24 a, and detects that the etching bath 1 is full of the etchantsince the nitrogen gas is discharged no more due to the blocked “HH”nitrogen tube 24 c, thereby stopping the supply of the etchant.

Subsequently, the nitrogen gas is put in the bubble plate 3 from the airsupply pipe 15 to generate bubbles, whereby an etching process of theglass substrates is carried out normally.

In this case, the guard 2 protects the etchant detect sensor 21 from thebubbles generated from the etchant, whereby the etchant maintains ahorizontal level. The etching process is performed normally when thenitrogen gas is discharged through the “HH” or “H” nitrogen tubes 24 cor 24 b. Yet, etching failure may occur when the nitrogen gas isdischarged through the “L” nitrogen tube 24 a.

Finally, when the etchant 25 is drained from the etching bath 1 afterthe completion of etching the glass substrate, the level of the etchantis lowered. Hence, the etching apparatus according to the related artrecognizes that the etchant is normally drained since the nitrogen gasis discharged through the “L(low)”, “H(high)”, and “HH(high high)”nitrogen tubes 24 a, 24 b, and 24 c, in order.

Unfortunately, the etching apparatus according to the related art hasthe following problems or disadvantages.

First of all, as the etching process is repeated, sludge as precipitatesof the glass etched by the etchant blocks at least one of the “L”, “H”,and “HH” nitrogen tubes of the etchant detect sensor to perform thesupply and discharge of the etchant abnormally. Hence, the etchingapparatus according to the related art can cause failure of the etchingprocess.

Secondly, when the “L” nitrogen tube is blocked, as shown at 26 in FIG.2, a cleaning process for cleaning the glass substrate with deionizedwater is carried out under the circumstance that the drain of theetchant is not completed. Hence, the etching apparatus according to therelated art causes degradation of the cleaning work since the deionizedwater as the cleaning material is mingled with the etchant.

Finally, the etching apparatus according to the related art consumescost and time for replacement of the components or periodical cleaningworks to prevent outlets of the “L”, “H”, and “HH” nitrogen tubes frombeing blocked by the sludge, thereby reducing productivity.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to an etching apparatusthat substantially obviates one or more problems due to limitations anddisadvantages of the related art.

An object of the present invention is to provide an etching apparatusenabling to increase productivity by detecting a level of an etchantsupplied inside an etching bath using a contact type optical sensor onan etching process of a glass substrate and having a deionized watertube for cleaning the contact type optical sensor after completion ofthe etching process of the glass substrate.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objectives and other advantages of the invention may berealized and attained by the structure particularly pointed out in thewritten description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with thepurpose of the invention, as embodied and broadly described herein, anetching apparatus according to the present invention includes an etchingbath having an etchant, a plurality of sensors inside the etching bathdetecting a level of the etchant, and a deionized water tube spraying adeionized water to the sensors.

Preferably, each of the sensors is a contact type optical sensordetecting whether to be contacted with an air or the etchant.

More preferably, the contact type optical sensor includes alight-emitting unit irradiating a light, a light-receiving unitdetecting the irradiated light from the light-emitting unit, and anoptical fiber having a conical or triangular end wherein the lightemitted from the light-emitting unit is reflected or refracted on theend to be transferred to the light-receiving unit or not.

More preferably, the optical fiber is formed of a TEFLON(polytetrafluoroethylene) based material.

More preferably, the optical fiber has an index of refraction similar tothat of the etchant.

Preferably, the sensor includes a first sensor detecting a level of theetchant and a second sensor detecting a maximum level of the etchant.

Preferably, the deionized water tube is installed horizontally over anupper side of the sensors.

Preferably, the etching apparatus further includes a guide fixed to abottom of the etching apparatus and porous and bubble plates supportedby the guide.

Preferably, the etchant is HF.

Preferably, the etching apparatus further includes an etchant supplytank supplying the etching bath with the etchant and a buffer tankdraining the etchant from the etching bath.

Accordingly, the etching apparatus according to the present inventionincludes the contact type optical sensors enabling to check the level ofthe etchant on the etching process of the substrates and the deionizedwater tube supplying the deionized water to clean the contact typeoptical sensors after completion of the etching process of the glasssubstrate, thereby enabling to wash out the sludge generated from theoptical sensor. Therefore, the present invention reduces periodicalcheck and cleaning, thereby enabling to increase productivity.

It is to be understood that both the foregoing general description andthe following detailed description of the present invention areexemplary and explanatory and are intended to provide furtherexplanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this application, illustrate embodiment(s) of the invention andtogether with the description serve to explain the principle of theinvention. In the drawings:

FIG. 1 illustrates a schematic cross-sectional view of an etchingapparatus according to a related art;

FIG. 2 illustrates a cross-sectional view of a nitrogen pressuredifference sensor according to a related art;

FIG. 3 illustrates a schematic cross-sectional view of an etchingapparatus according to the present invention; and

FIG. 4 illustrates a bird's-eye view of a deionized water tube andoptical sensors according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. Wherever possible, the same reference numbers will be usedthroughout the drawings to refer to the same or like parts.

FIG. 3 illustrates a schematic cross-sectional view of an etchingapparatus according to the present invention.

Referring to FIG. 3, an etching apparatus according to the presentinvention includes an etching bath 101 holding an etchant therein, anetchant supply tank 109 supplying the etching bath 101 with the etchant,a buffer tank 111 filtering to store temporarily the etchant completingan etching process in the etching bath 101, a plurality of contact typeoptical sensors 103 a and 103 b installed inside the etching bath 101 todetect levels of the etchant supplied and discharged from the etchantsupply tank 109 and the buffer tank 111, respectively, and a deionizedwater tube 105 having at least one deionized water hole(not shown in thedrawing) spraying a deionized water to clean the contact type opticalsensors 103 a and 103 b.

And, the etching apparatus further includes a supporter 106 installed tobe fixed to a bottom surface of the etching bath 101, a porous platesupported by the supporter 106 to support a glass substrate, a bubbleplate 108 supported by the supporter 106 to be in parallel with theporous plate 107, and a gas supply pipe 110 supplying the bubble plate108 with a nitrogen (N₂) gas.

A plurality of glass substrate(not shown in the drawing) that will beetched are stood straight on the porous plate 107 with a predeterminedinterval from each other, and are dipped in the etchant filling up theetching bath 101 for etching. Bubbles are generated from the bubbleplate 103 by the nitrogen gas supplied from the gas(air) supply pipe 110and the etchant circulates uniformly by the bubbles ascending betweenthe glass substrates. Thus, the glass substrates can be etched evenly.

Moreover, a guard 102, to which a plurality of the contact type opticalsensors 103 a and 103 b and the deionized water tube 105 are fixed, hasa structure that front and rear sides in the drawing are open. If theetchant is supplied over a predetermined level, the etchant is putinside the guard 102.

And, a plurality of the contact type optical sensors 103 a and 103 bdetecting the level of the etchant supplied inside the etching bath 101are detecting sensors using a difference of refractive index. Each ofthe contact type optical sensors 103 a and 103 b includes alight-emitting unit for irradiating a light, a light-receiving unitdetecting the irradiated light from the light-emitting unit, and anoptical fiber made of a TEFLON (polytetrafluoroethylene) material havingexcellent oil and chemical withstanding properties to have a conical ortriangular end wherein the light emitted from the light-emitting unit isreflected or refracted on the end to be transferred to thelight-receiving unit or not in accordance with an external state.

Each of the contact type optical sensors 103 a and 103 b makes use ofthe principle that: a light goes straight in a medium having a constantindex of refraction; and a portion of the light transmits but the otherportion is reflected on a boundary between two adjacent mediums havingdifferent refraction indexes, respectively. Hence, the optical fiber ismade of a material having a refraction index similar to that of theetchant so that the light is reflected on the end contacted with an airor is irradiated from the end contacted with the etchant.

Namely, each of the contact type optical sensors 103 a and 103 b has theoptical fiber made of the TEFLON (polytetrafluoroethylene) materialhaving a refraction index similar to that of a liquid and makes its endconical or triangular shape. Hence, the light emitted from thelight-emitting unit becomes incident along the optical fiber in the air,and is refracted on two sides of the cone or triangle as the refractionboundary area of the end contacted with the air to be detected by thelight-receiving unit. In the liquid, the light incident on the opticalfiber is refracted(irradiated) on the end of the optical fiber since therefraction indexes of the optical fiber and etchant are similar to eachother. Hence, the light fails to be reflected on the light-receivingunit.

In this case, a detecting signal is controlled to output ‘no’ if thecontact type optical sensors 103 a and 103 b are contacted with the airoutputs, but ‘yes’ if the contact type optical sensors 103 a and 103 bare contacted with the liquid.

Therefore, the etching apparatus according to the present inventionenables to control the level of the etchant which is being supplied intothe etching bath using the contact type optical sensors 103 a and 103 bmaking use of the difference of refraction indexes between the air andliquid.

FIG. 4 illustrates a bird's-eye view of a deionized water tube andoptical sensors according to the present invention.

Referring to FIG. 4, each of “H” and “HH” optical sensors 103 a and 103b is stood straight to detect a level of an etchant supplied into theetching bath (‘101’ in FIG. 3). And, a deionized water tube 105 having aplurality of deionized water holes 105 a spraying deionized water toclean the contact type optical sensors 103 a and 103 b is disposed overthe “H” and “HH” optical sensors 103 a and 103 b horizontally.

In this case, a diameter of the deionized water tube 105 is about 4 mm,and cleans a plurality of the contact type optical sensors 103 a and 103b not by being supplied with the deionized water if the etchant existsin the etching bath 101 but by being supplied with the deionized waterif there is no etchant in the etching bath 101.

It may happen that sludge generated from the etchant on the etchingprocess sticks to the contact type optical sensors. Yet, the presentinvention enables to remove cleanly the sludge by the deionized watersupplied from the deionized water tube as soon as the etching process iscompleted.

An etching process using the above-constituted etching apparatus of thepresent invention is explained as follows.

First of all, a plurality of glass substrates are stood straight on theporous plate 107, and the etchant stored with a predeterminedconcentration in an etchant mixing tank(not shown in the drawing) issupplied into the etching bath 101. Once a predetermined quantity of theetchant is supplied to the etching bath 101 to have the “H” contact typeoptical sensor 103 a dipped in the etchant, the “H” contact type opticalsensor 103 a recognizes that a proper quantity of the etchant has beensupplied thereto.

In this case, the etchant is preferably HF.

Subsequently, when the etchant is kept being supplied to the etchingbath 101 to have the “HH” contact type optical sensor 103 b dipped inthe etchant, the “HH” contact type optical sensor 103 b detects that theetchant is supplied excessively to stop supplying the etchant.

Simultaneously, the nitrogen gas is injected into the bubble plate 108to produce bubbles. The bubbles then penetrates the holes of the porousplates 107 to make the etchant circulate in the etching bath 101,whereby the glass substrates are etched.

In this case, a temperature measuring device is further installed insidethe etching apparatus to measure the temperature caused by exothermicreaction between the substrates and etchant. Hence, the glass substratescan be etched evenly.

The etching process is then carried out on the glass substrates for apredetermined time. After the etching of the glass substrates has beenfinished, the etchant used for the etch of the glass substrates startsto be drained. Once the “H” contact type optical sensor 103 a is exposedto the air, it is detected by the “H” contact type optical sensor 103 athat the etchant is being drained.

In this case, vaporization of the etchant during the etching process ofthe glass substrates can decrease the etchant to expose the “HH” contacttype optical sensor 103 b to the air. Hence, it is possible to ignorethe detection of the “HH” contact type optical sensor 103 b.

Thereafter, the etchant is completely removed from the etching bath 101to finish the etching process of the glass substrates. The glasssubstrates and etching bath 101 are then cleaned to remove the etchantusing the deionized water.

In this case, if the etching process of the glass substrates iscompleted, the deionized water tube 105 is supplied with the deionizedwater to clean the “H” and “HH” contact type optical sensors 103 a and103 b. Moreover, the “H” and “HH” contact type optical sensors 103 a and103 b are kept being cleaned until a next etching process of anotherglass substrates is initiated.

Thus, the etching apparatus according to the present invention enablesto detect the level of the etchant in the etching bath 101 using thecontact type optical sensors 103 a and 103 b as well as clean thecontact type optical sensors using the deionized water tube 105 to whichthe deionized water is supplied all the time after the completion of theetching process of the glass substrates. Therefore, the presentinvention enables to increase productivity in accordance withmaintenance of the etching apparatus.

Accordingly, the etching apparatus according to the present inventionincludes the contact type optical sensors enabling to check the level ofthe etchant on the etching process of the glass substrates and thedeionized water tube supplying the deionized water to clean the contacttype optical sensors after completion of the etching process of theglass substrates, thereby enabling to increase productivity inaccordance with maintenance of the etching apparatus.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in the present invention. Thus,it is intended that the present invention covers the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

1. An etching apparatus comprising: an etching bath having an etchant; aplurality of sensors inside the etching bath for detecting a level ofthe etchant; a deionized water tube for spraying a deionized water tothe sensors; a guard having an opening and formed on an inner wall ofthe etching bath, wherein the sensors and the deionized water tube arefixed to the guard; a guide fixed to a bottom of the etching apparatus;and a porous plate and a bubble plate supported by the guide.
 2. Theapparatus of claim 1, wherein each of the sensors is a contact typeoptical sensor detecting contact with air or the etchant.
 3. Theapparatus of claim 2, wherein the contact type optical sensor comprises;a light-emitting unit irradiating a light; a light-receiving unitdetecting the irradiated light from the light-emitting unit; and anoptical fiber having a conical or triangular end wherein the lightemitted from the light-emitting unit is reflected or refracted on theend to be transferred to the light-receiving unit or not.
 4. Theapparatus of claim 3, wherein the optical fiber includespolytetrafluoroethylene.
 5. The apparatus of claim 3, wherein theoptical fiber has an index of refraction similar to that of the etchant.6. The apparatus of claim 1, wherein the sensors comprise a first sensordetecting a level of the etchant and a second sensor detecting a maximumlevel of the etchant.
 7. The apparatus of claim 1, wherein the etchantis HF.
 8. The apparatus of claim 1, further comprising: an etchantsupply tank supplying the etching bath with the etchant; and a buffertank draining the etchant from the etching bath.
 9. An etching apparatuscomprising: an etching bath having an etchant; a plurality of sensorsinside the etching bath detecting a level of the etchant; a deionizedwater tube spraying a deionized water to the sensors, wherein thedeionized water tube is installed horizontally over an upper side of thesensors; and a guard having an opening and formed on an inner wall ofthe etching bath, wherein the sensors and the deionized water tube arefixed to the guard.
 10. An etching apparatus for etching glasssubstrates for a liquid crystal display comprising: an etching bathhaving an etchant, the etchant having a sludge generated during theetching of the glass substrates; a porous plate and a bubble plate inthe etching bath for detaching the sludge from the glass substratesduring the etching; a plurality of sensors inside the etching bath fordetecting a level of the etchant; a deionized water tube for spraying adeionized water to the sensors so as to remove the sludge stuck to thesensors; and a guard having an opening and formed on an inner wall ofthe etching bath, wherein the sensors and the deionized water tube arefixed to the guard.